South Korean officials say North Korea appears to be preparing for more nuclear and missile tests, following a nuclear test in February that triggered tightened U.N. sanctions.
Lawmakers at a South Korean National Assembly committee meeting on Monday asked Unification Minister Ryoo Kihl-jae about nuclear activity.
Ryoo confirmed that there are signs of preparation activity at the Punggye-ri nuclear test site, but he would not comment further on matters related to intelligence.
On Sunday, Kim Jang-soo - chief national security adviser to President Park Geun-hye, said a missile test or some other provocation could come before or after Wednesday, the date by which the North has suggested diplomats leave the capital, Pyongyang.
He said the North's real objective is to force diplomatic concessions from Washington and Seoul, but added that South Korea is maintaining its military readiness whether or not Pyongyang's threats "are merely rhetoric."